Sharp transitions in microclimatic conditions between savanna and forest in New Caledonia: Insights into the vulnerability of forest edges to fire

• Published in: Austral ecology Vol. 38; no. 6; pp. 680 - 687
• Main Authors: Ibanez, Thomas, Hély, Christelle, Gaucherel, Cédric
• Format: Journal Article
• Language: English
• Published: Carlton Blackwell Publishing Ltd 01.09.2013; Blackwell; Wiley
• Subjects: Air temperature; Biological and medical sciences; boundary; Drought; ecotone; edge effect; El Nino; Forest & brush fires; Forest and land fires; Forest protection; forest understorey; Forestry; Forests; Fundamental and applied biological sciences. Psychology; General forest ecology; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; Grasslands; La Nina; Life Sciences; Microclimate; Phytopathology. Animal pests. Plant and forest protection; Prescribed fire; Relative humidity; Savannahs; Tropical environments; Vapor pressure; vapour pressure deficit; Weather damages. Fires; New Caledonia; Melanesia; Oceania; ISEW, Pacific, New Caledonia; boundary; Forests; Forest edge; Savannah; Tropical zone; Water deficit; Vulnerability; forest understorey; Ecotone; Edge effect; Understory; Transition; Forest fire; vapour pressure deficit; TROPICAL RAIN-FOREST; ecotone; AMAZONIAN FORESTS; edge effect
• ISSN: 1442-9985; 1442-9993
• DOI: 10.1111/aec.12015

Fires are one of the main causes of forest loss in the tropics. Understanding the dynamic edge effects is critical for managing fires and protecting forests. We measured and analysed trends in microclimatic conditions (air temperature, relative humidity and vapour pressure deficit) over 7 months along three transects extending from core savanna areas to core forest areas. We tested two hypotheses: (i) that the forest edge is subject to microclimatic edge effects, and (ii) that the depth of these edge effects increases during dry periods. Sharp changes in each microclimatic variable were consistently observed between savanna and forest throughout the study period. Microclimatic transitions took place within 5 m outside the forest boundary. Drought levels increased homogenously throughout the forest and were not disproportionately severe in the vicinity of the forest edge. We suggest that these results were related to the fact that the studied period was abnormally humid due to a La Niña episode, and that under such conditions the vulnerability of the forest edge to savanna fires is relatively low. Relatively wet conditions in the savanna close to the forest edge may promote forest expansion by limiting fire spread. Prescribed fires during humid years could reduce fuel loads in savanna without affecting the forest edge, which would prevent fires during the dry years associated with El Niño episodes from having severe impacts.